feat(editor): add Save & Close next to Save in the embedded editor

[erseco]

Stack 6/6, based on #129.

What

• Save saves the package and keeps the embedded editor open (unchanged).
• Save & Close, next to Save, runs the same save() and waits for it. It returns to Files (the same place as the "←" link) only after the write succeeded. A failed save shows the usual alert and keeps the editor open.
• No double saves: save() now resolves true/false and ignores calls while a save is in flight. That one guard covers repeated clicks, Ctrl/Cmd+S (fix(editor): make Ctrl/Cmd+S save from inside the embedded editor #126) and Save & Close. Both buttons are disabled during a save.

UI

The toolbar uses plain buttons with inline MDI icons and has no dropdown component, so this adds two adjacent buttons instead of a split button:

• Save: primary, existing content-save icon.
• Save & Close: outline style, MDI logout icon. No standalone X icon.

Closing with unsaved changes

There was no protection before, and the editor's postMessage protocol exposes no dirty/unsaved state. Adding one would need new state tracking, so it's left out.

Tests

tests/js/elpx-view-page.test.ts checks that:

• Save keeps the editor open.
• Save & Close closes only after the save resolves.
• Save & Close stays open when the save fails.
• Repeated or concurrent saves call the editor once.

Vitest now loads .vue files through @vitejs/plugin-vue. It was already installed via @nextcloud/vite-config and is now an explicit dev dependency.

Compatibility with open PRs

• Builds on fix(editor): make Ctrl/Cmd+S save from inside the embedded editor #126 (Ctrl+S → save()) and refactor: drop the unreachable standalone editor page and dead fields #127 (single save path in ElpxViewPage).
• The draft Secure opaque-origin viewer and editor preview #68 touches only src/viewer/ElpxViewer.vue on the frontend, so no overlap.

Verification

composer install                 exit 0
npm install                      exit 0
npm run typecheck                exit 0
npm test                         Tests 147 passed (147)
npm run lint                     exit 0
npm run lint:biome               9 warnings, 1 info (same as on main)
npm run build                    ✓ built
npx vitest run --coverage        All files 98.58 % lines, 93.54 % branches
make architecture-check          Architecture records OK — 3 records, 0 changes.
make -n download-editor … typecheck   exit 0
vendor/bin/phpunit               OK (115 tests, 311 assertions)
composer cs:check                Found 0 of 32 files that can be fixed
git diff --check                 clean

Not yet exercised in a live Nextcloud.

[github-actions]

Preview this PR in the Nextcloud Playground

A fresh Nextcloud boots in your browser with this branch's exelearning app installed and enabled (log in as admin / admin). Two sample .elpx are seeded under exelearning-samples/ in Files — click one to open the viewer.

eXeLearning editor: v4.0.5 (overlaid at boot from the upstream release).

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.81%. Comparing base (52fc162) to head (383884b).

Additional details and impacted files

@@                     Coverage Diff                     @@
##             chore/tests-tooling-docs     #131   +/-   ##
===========================================================
  Coverage                       93.81%   93.81%           
  Complexity                        149      149           
===========================================================
  Files                              25       25           
  Lines                             776      776           
  Branches                           89       89           
===========================================================
  Hits                              728      728           
  Misses                             35       35           
  Partials                           13       13           

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